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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Angiotensin II (Ang II) stimulates norepinephrine transporter (NET) and tyrosine hydroxylase (TH) in the neurons, but the signal transduction mechanism of this neuromodulation is not understood. Treatment of neuronal cultures of hypothalamus-brainstem with Ang II resulted in a time- and dose-dependent activation of Ras, Raf-1, and mitogen-activated protein kinase. This activation was mediated by the interaction of Ang II with the AT1, receptor subtype and was associated with the redistribution of AT1 receptor with Ras and Raf-1 on the neuronal membrane. Treatment with antisense oligonucleotide (AON) to mitogen-activated protein kinase decreased mitogen-activated protein kinase immunoreactivity by 70% and attenuated Ang II stimulation of c-fos, NET, and TH mRNA levels. This demonstrates that induction of these genes requires mitogen-activated protein kinase activation by Ang II. In contrast, AON to mitogen-activated protein kinase failed to inhibit Ang II stimulation of plasminogen activator inhibitor-1 mRNA levels. These results suggest that AT1 receptors are coupled to a Ras-Raf-1 mitogen-activated protein kinase signal transduction pathway that is responsible for stimulation of NET and TH, two neuro-modulatory actions of Ang II in the brain.
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PMID:Regulation of neuromodulatory actions of angiotensin II in the brain neurons by the Ras-dependent mitogen-activated protein kinase pathway. 875 67

In the present study we investigated the regulation of tyrosine hydroxylase (TH) by angiotensin II (Ang II) in an attempt to provide cellular and molecular evidence that this hormone has increased neuromodulatory actions in the spontaneously hypertensive (SH) rat brain. Neuronal cells in primary culture from the hypothalamus-brain stem of both normotensive [Wistar-Kyoto (WKY)] and SH rats have been used. These cultures mimic in vivo situations. Ang II caused a time-dependent increase in TH activity in WKY rat brain neurons. A maximal increase of 2.5-fold was observed with 100 nM Ang II in an actinomycin- and cycloheximide-dependent process. In addition, Ang II caused a parallel increase in TH messenger RNA (mRNA) levels, with a maximal stimulation of 5-fold in 4 h by 100 nM Ang II in WKY rat brain neurons. The stimulation of TH mRNA was mediated by the AT1 receptor subtype, resulted from an increase in its transcription, and involved activation of phospholipase C and protein kinase C. Antisense oligonucleotide for c-fos attenuated Ang II stimulation of TH mRNA in a time- and dose-dependent fashion, indicating an involvement of c-fos as a putative third messenger in Ang II stimulation of TH. Ang II also caused stimulation of TH activity and its mRNA levels in neuronal cultures of SH rat brain by a mechanism similar to that observed for neuronal cultures of WKY rat brain, involving AT1 receptors, protein kinase C, and c-fos. However, the stimulation of TH activity and that of TH mRNA were approximately 30% and 80% higher, respectively, in the SH rat brain neurons than those in the WKY rat brain neurons. In vivo experiments have been carried out to validate the elevated response of TH gene expression to Ang II in SH rat brain neuronal cultures. Ang II stimulated both TH activity and TH mRNA levels in the hypothalami and brain stems of adult WKY and SH rats. The level of stimulation in the brain of the SH rat was significantly higher than that in the WKY rat. These observations are consistent with an increase in AT1, receptor gene expression and suggest that increased TH gene expression could be the cellular/molecular basis for the greater neuromodulatory action of Ang II in the SH rat brain.
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PMID:Angiotensin II regulation of tyrosine hydroxylase gene expression in the neuronal cultures of normotensive and spontaneously hypertensive rats. 875 88

Angiotensin II (Ang II) stimulates expression of tyrosine hydroxylase and norepinephrine transporter genes in brain neurons; however, the signal-transduction mechanism is not clearly defined. This study was conducted to determine the involvement of the mitogen-activated protein (MAP) kinase signaling pathway in Ang II stimulation of these genes. MAP kinase was localized in the perinuclear region of the neuronal soma. Ang II caused activation of MAP kinase and its subsequent translocation from the cytoplasmic to nuclear compartment, both effects being mediated by AT1 receptor subtype. Ang II also stimulated SRE- and AP1-binding activities and fos gene expression and its translocation in a MAP kinase-dependent process. These observations are the first demonstration of a downstream signaling pathway involving MAP kinase in Ang II-mediated neuromodulation in noradrenergic neurons.
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PMID:Angiotensin II regulation of neuromodulation: downstream signaling mechanism from activation of mitogen-activated protein kinase. 897 26

MAP kinase stimulation is a key signaling event in the AT1 receptor (AT1R)-mediated chronic stimulation of tyrosine hydroxylase and norepinephrine transporter in brain neurons by angiotensin II (Ang II). In this study, we investigated the involvement of MAP kinase in AT1R phosphorylation to further our understanding of these persistent neuromodulatory actions of Ang II. Ang II caused a time-dependent phosphorylation of neuronal AT1R. This phosphorylation was associated with internalization and translocation of AT1R into the nucleus. MAP kinase also stimulated phosphorylation of neuronal AT1R. The conclusion that MAP kinase participates in neuronal AT1R phosphorylation and its targeting into the nucleus is supported further by the following. (1) MAP kinase-mediated phosphorylation of AT1R was blocked by the AT1R antagonist losartan; (2) AT1R co-immunoprecipitated with MAP kinase; (3) MAP kinase-kinase inhibitor PD98059 attenuated Ang II-induced phosphorylation of AT1R; and (4) PD98059 blocked Ang II-induced nuclear translocation of AT1Rs. In summary, these observations demonstrate that Ang II-induced phosphorylation of AT1R is mediated by its activation of MAP kinase. A possible role of AT1R translocation into the nucleus on persistent neuromodulatory actions of Ang II has been discussed.
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PMID:Involvement of MAP kinase in angiotensin II-induced phosphorylation and intracellular targeting of neuronal AT1 receptors. 903 Jun 25

There exist at least two distinct subtypes of angiotensin II receptors in the brain, namely the AT1 and AT2 subtypes. The high density of angiotensin II AT1 receptors is present in the medulla oblongata. The AT1 subtype of angiotensin II receptors mainly mediates central cardiovascular events. In the present study a polyclonal antibody against the angiotensin II AT1 receptor and a monoclonal antibody against tyrosine hydroxylase were employed to evaluate the possible presence of angiotensin II AT1 receptor-like immunoreactivity in the catecholaminergic neurons of the rat medulla oblongata by means of the double colour immunofluorescence technique. A weak, diffuse cytoplasmic angiotensin II AT1 receptor-like immunoreactivity was observed in almost all the catecholaminergic cell bodies of the A2, C1, C2 and C3 cell groups, except those of the A1 cell group containing moderately intense, diffuse cytoplasmic angiotensin II AT1 receptor-like immunoreactivity, occasionally found in the noradrenergic dendrites of the A1 cell group. There was a higher density of the angiotensin II AT1 receptor-like immunoreactive profiles in the A2 cell group area than in other catecholaminergic cell group areas. In addition, the angiotensin II AT1 receptor-like immunoreactivity was seen in non-catecholaminergic neurons. The present results provide evidence for the existence of the specific angiotensin II AT1 receptor-like immunoreactivity in the noradrenergic and adrenergic neurons of the rat medulla oblongata known to have a cardiovascular role. Thus, the findings support the view that angiotensin II AT1 receptors in the medulla oblongata participate in cardiovascular control and indicate a cellular substrate for the documented interaction between the angiotensin II and adrenergic transmission lines in cardiovascular function at the level of the nucleus tractus solitarii.
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PMID:Localization of angiotensin II AT1 receptor-like immunoreactivity in catecholaminergic neurons of the rat medulla oblongata. 930 Apr 37

Brain angiotensin II (Ang II) inhibits pituitary prolactin release by an indirect mechanism requiring stimulation of dopamine formation and release. We report that [125I]Sar1-Ang II binding to AT1 receptors and AT1A receptor mRNA expression increase selectively in the dorsomedial arcuate nucleus of 17beta-estradiol-primed ovariectomized rats after treatment with progesterone. In hormone-treated rats, arcuate nucleus AT1A receptor mRNA expression is associated with tyrosine hydroxylase-positive neurons. No AT1A receptor mRNA was detected in tyrosine hydroxylase-positive cells of the arcuate nucleus of intact male rats. Conversely, in the anterior pituitary, where local or circulating Ang II stimulates prolactin release, [125I]Sar1-Ang II binding to AT1 receptors and AT1B receptor mRNA expression are decreased in 17beta-estradiol/progesterone-treated ovariectomized rats. Thus, AT1A receptors in the dorsal arcuate nucleus and AT1B receptors in the anterior pituitary are regulated inversely by estrogen/progesterone treatment, supporting the hypothesis of a dual role for brain and pituitary Ang II on prolactin release. The colocalization of AT1A receptor mRNA and tyrosine hydroxylase in neurons of the arcuate nucleus furthermore indicates that within this area central Ang II acts directly on dopaminergic neurons. These results support the hypothesis that central Ang II inhibits pituitary prolactin release indirectly via modulation of dopaminergic activity in the arcuate nucleus.
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PMID:Angiotensin II AT1A receptor mRNA expression is induced by estrogen-progesterone in dopaminergic neurons of the female rat arcuate nucleus. 933 3

Angiotensin II (Ang II) interaction with the neuronal AT1 receptor results in a chronic stimulation of neuromodulation that involves the expression of norepinephrine transporter (NET) and tyrosine hydroxylase (TH). In view of this unique property and the presence of putative nuclear localization signal (NLS) consensus sequence in the AT1 receptor, this study was conducted to investigate the hypothesis that Ang II would induce nuclear sequestration of this G protein-coupled receptor and that the sequestration may have implications on Ang II-induced expression of NET and TH genes. Incubation of neuronal cultures with Ang II caused a time- and dose-dependent increase in the levels of AT1 receptor immunoreactivity in the nucleus. A 6.7-fold increase was observed with 100 nM Ang II, in 15 min, that was blocked by losartan, an AT1 receptor-specific antagonist. Ang II-induced nuclear sequestration was specific for AT1 receptor, because Ang II failed to produce a similar effect on neuronal AT2 receptors. The presence of the putative NLS sequence in the cytoplasmic tail of the AT1 receptor seems to be the key in nuclear targeting because: 1) nuclear targeting was attenuated by a peptide of the AT1 receptor that contained the putative NLS sequence; and 2) Ang II failed to cause nuclear translocation of the AT2 receptor, which does not contain the putative NLS. Ang II also caused a time- and dose-dependent stimulation of P62 phosphorylation, a glycoprotein of the nuclear pore complex. A 6-fold stimulation of phosphorylation was observed with 100 nM Ang II, in 15 min, that was completely blocked by losartan and not by PD123,319, an AT2 receptor specific antagonist. Preloading of neurons with p62-pep (a peptide containing consenses of mitogen-activated protein kinase in p62) resulted in a loss of Ang II-induced p62 phosphorylation and stimulation of NET and TH messenger RNA levels. In conclusion, these data demonstrate that Ang II induces nuclear sequestration of AT1 receptor involving NLS in the AT1 receptor and p62 of the nuclear pore complex in brain neurons. A possible role of such a nuclear targeting of the AT1 receptor on chronic neuromodulatory actions of Ang II has been discussed.
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PMID:Angiotensin II-induced nuclear targeting of the angiotensin type 1 (AT1) receptor in brain neurons. 942 35

Chronic stimulation of brain neurons by angiotensin II (Ang II) results in a increase in norepinephrine (NE) uptake. This involves stimulation of transcription of NE transporter and tyrosine hydroxylase genes and is associated with translocation of signaling molecules and transcription factors from the cytoplasmic compartment into the neuronal nucleus (). We report here that the phosphorylation of p62, a glycoprotein nucleoporin of the nuclear pore complex (NPC), by MAP kinase is involved in this process. Ang II caused a time-dependent translocation of signal transducers and activators of transcription (STAT3) from the cytoplasmic compartment into the nucleus. This translocation was attenuated by pretreatment with antisense oligonucleotide (AON) to MAP kinase. Ang II also stimulated phosphorylation of p62, and a maximal phosphorylation of 12-fold was observed with 100 nM Ang II. This stimulation was blocked by losartan, an AT1 receptor subtype-specific antagonist. The conclusion that MAP kinase is involved in Ang II-induced phosphorylation of p62 and nuclear translocation of STAT3 is supported by the following. (1) p62 phosphorylation was blocked by a peptide that competes with p62 as a MAP kinase substrate both in vitro and in vivo; (2) AON to MAP kinase attenuated Ang II stimulation of p62 phosphorylation; and (3) in addition, it also blocked nuclear translocation of STAT3. Intracellular loading of the peptide containing MAP kinase substrate consensus of the p62 reduced Ang II stimulation of p62 phosphorylation and nuclear translocation of STAT3 in both in vivo and in vitro experiments. These observations suggest that Ang II-induced phosphorylation of p62 may accelerate the activity of the NPC, which would result in an increase in the nuclear transport of transcription factors and signaling molecules. This will stimulate transcriptional processes associated with Ang II regulation of NE neuromodulation.
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PMID:Involvement of p62 nucleoporin in angiotensin II-induced nuclear translocation of STAT3 in brain neurons. 945 42

The objective of this review is to examine the role of neuronal angiotensin II (Ang II) receptors in vitro. Two types of G protein-coupled Ang II receptors have been identified in cardiovascularly relevant areas of the brain: the AT1 and the AT2. We have utilized neurons in culture to study the signaling mechanisms of AT1 and AT2 receptors. Neuronal AT1 receptors are involved in norepinephrine (NE) neuromodulation. NE neuromodulation can be either evoked or enhanced. Evoked NE neuromodulation involves AT1 receptor-mediated, losartan-dependent, rapid NE release, inhibition of K+ channels and stimulation of Ca2+ channels. AT1 receptor-mediated enhanced NE neuromodulation involves the Ras-Raf-MAP kinase cascade and ultimately leads to an increase in NE transporter, tyrosine hydroxylase and dopamine beta-hydroxylase mRNA transcription. Neuronal AT2 receptors signal via a Gi protein and are coupled to activation of PP2A and PLA2 and stimulation of K+ channels. Finally, putative cross-talk pathways between AT1 and AT2 receptors will be discussed.
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PMID:Angiotensin receptors and norepinephrine neuromodulation: implications of functional coupling. 955 76

The objective of this review is to examine the role of neuronal angiotensin II (Ang II) receptors in vitro. Two types of G protein-coupled Ang II receptors have been identified in cardiovascularly relevant areas of the brain: the AT1 and the AT2. We have utilized neurons in culture to study the signaling mechanisms of AT1 and AT2 receptors. Neuronal AT1 receptors are involved in norepinephrine (NE) neuromodulation. NE neuromodulation can be either evoked or enhanced. Evoked NE neuromodulation involves AT1 receptor-mediated, losartan-dependent, rapid NE release, inhibition of K+ channels and stimulation of Ca2+ channels. AT1 receptor-mediated enhanced NE neuromodulation involves the Ras-Raf-MAP kinase cascade and ultimately leads to an increase in NE transporter, tyrosine hydroxylase and dopamine beta-hydroxylase mRNA transcription. Neuronal AT2 receptors signal via a Gi protein and are coupled to activation of PP2A and PLA2 and stimulation of K+ channels. Finally, putative cross-talk pathways between AT1 and AT2 receptors will be discussed.
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PMID:Angiotensin receptors and norepinephrine neuromodulation: implications of functional coupling. 965 73


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